Engine Surge after start

[Zoidberg]

Hi! My 2008 128i has been suffering from a problem for the past few months. Sometimes (not always) after a cold start, the engine maintains 5000 or 6000RPM at idle for about 5 minutes until the engine has warmed-up.

It happens randomly, and it DOES NOT seem related to cold weather, but after the engine is warmed-up, the issue is resolved. This morning, I started with the temperature being -10C (15F) and the idle was normal. It DOES seem to occur more frequently after the car has been sitting a long time (2-3 days) and happens more often when the humidity is high.

There are no codes. I don't even know where to start looking on what could cause this problem. I'm pretty sure there is no vacuum leak. Maybe bad ignition coils? MAF? As I mentioned, there are no codes.

Any ideas would be appreciated!

[Mr Gasser]

Next time you start it, open the hood and spray some brake cleaner around the engine and see if the RPM changes... if it does, maybe a leaky gasket, possible the intake manifold...how many miles?

[Zoidberg]

I will try that. Car has 105,000 miles. I'm the original owner.

[MightyMouseTech]

Wait, 5-6000 RPM? Seriously? And the engine hasn't sent a rod through through the block doing that? Do you have aftermarket floor mats, or even worse, have a couple sets of floor mats installed? Floor mat pressing on accelerator?

[Dackelone]

A generic code reader won't read/see the BMW shadow codes. You need an App like Carly or MHD to read the BMW specific codes.

Something is really wrong IF you engine revs up to 5K on cold start. That's not good for the engine.

Perhaps you should start by dropping your car off at a dealer or indi shop.

[Mr Gasser]

MAF sensor dirty? vacuum hoses brittle?105,000 miles is a lot, could be the 100,000 miles blues kicking in.